If you look closely, it appears to be a mashup of the VMP and Dingo, both appearing in Call of Duty: Black Ops III.
The main differences are that the SMG mode makes the VMP's magazine protrude, then bend at an L-shaped angle, as well as adding more parts. The LMG mode has arranged the Dingo with a vertical grip, as well as a belt feed instead of a connecting arm on the magazine.